Positive electrode active material, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material capable of improving the performance of a lithium secondary battery, and a positive electrode and a lithium secondary battery comprising same, wherein the positive electrode active material comprises a lithium iron manganese phosphate compound in which the content of manganese (Mn) is less than 50 mol% among all metals excluding lithium, and has an average particle diameter (D50) of 400 nm to 900 nm, the lithium iron manganese phosphate compound including magnesium (Mg) and a doping element (M), wherein the doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V), and the content of magnesium (Mg) in the lithium iron manganese phosphate compound is 500 ppm to 1,500 ppm, with respect to the total weight of the lithium iron manganese phosphate compound.

Description

Anode active material, and anode and lithium secondary battery including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0123320 filed September 10, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a positive electrode active material, and a positive electrode and a lithium secondary battery comprising the same.

[0006]

[0007] With the recent increase in technological development and demand for mobile devices and electric vehicles, the demand for rechargeable batteries as an energy source is rapidly rising. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rates, have been commercialized and are widely used.

[0008] Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material included in the positive electrode plays a significant role in determining the battery's capacity, output, and lifespan. Improving the performance of the positive electrode active material is essential for lithium secondary batteries to achieve high energy density, output, and lifespan; consequently, much research has recently been conducted to develop high-performance positive electrode active materials.

[0009] Lithium transition metal oxides, such as lithium cobalt-based oxides like LiCoO2, lithium nickel-based oxides like LiNiO2, lithium manganese-based oxides like LiMnO2 or LiMn2O4, and lithium iron phosphate compounds like LiFePO4, have been developed as cathode active materials for lithium secondary batteries, and recently, Li[Ni a Co b Mnc ]O2, Li[Ni a Co b Al c ]O2, Li[Ni a Co b Mn c Al d Lithium composite transition metal oxides containing two or more transition metals, such as O2, have been developed and are widely used.

[0010] Meanwhile, lithium iron phosphate compounds having an olivine structure are promising active materials that have excellent lifespan characteristics and superior safety features, including overcharging and over-discharging, because they have the best structural stability.

[0011] In particular, LiFePO4 exhibits excellent high-temperature stability due to the strong bonding strength of PO4. Furthermore, because it contains iron, which is resource-abundant and inexpensive, it is cheaper than the aforementioned LiCoO2, LiNiO2, or LiMn2O4, and has low toxicity, resulting in minimal environmental impact. However, since LiFePO4 has low electrical conductivity, using it as a cathode active material leads to an increase in the battery's internal resistance. Consequently, the battery capacity decreases as the polarization potential increases during circuit closure. Additionally, LiFePO4 has a low average operating voltage, resulting in low energy density.

[0012] To address this, there have been attempts to use LiFePO4 doped with manganese. However, when manganese-doped LiFePO4—that is, when a manganese-based lithium iron phosphate compound—is applied to a battery, the average operating voltage increases and energy density improves; yet, manganese ion leaching occurs during charging and discharging. This issue poses a problem for applications in fields where lifespan and power characteristics are particularly critical.

[0013]

[0014] The present invention aims to solve the above-mentioned problems by providing a positive electrode active material capable of reducing manganese leaching and improving lifespan characteristics, capacity characteristics, resistance characteristics, and charging efficiency.

[0015] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery having excellent lifespan characteristics, including the positive electrode active material as described above.

[0016]

[0017] (1) The present invention comprises a lithium iron manganese phosphate compound having a manganese (Mn) content of less than 50 mol% among all metals excluding lithium, wherein the lithium iron manganese phosphate compound comprises magnesium (Mg) and a doping element (M), wherein the doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V), and the magnesium (Mg) content in the lithium iron manganese phosphate compound is 500 ppm or more and 1,500 ppm or less with respect to the total weight of the lithium iron manganese phosphate compound, and the average particle size (D 50 Provides a positive electrode active material having a diameter of 400 nm or more and 900 nm or less.

[0018] (2) The present invention provides a positive electrode active material according to (1), wherein the lithium iron phosphate manganese-based compound has a manganese (Mn) content of 25 mol% or more and 35 mol% or less among all metals excluding lithium.

[0019] (3) The present invention provides a positive electrode active material in which, in (1) or (2), the content of the doping element (M) in the lithium iron phosphate manganese-based compound is 800 ppm or more and 5,000 ppm or less with respect to the total weight of the lithium iron phosphate manganese-based compound.

[0020] (4) The present invention provides a positive electrode active material in which, in any one of (1) to (3), the lithium iron phosphate manganese-based compound has a composition represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li 1+y1 Fe1-p1-q1-q2Mn p1 Mg q1 M 1 q2 (PO4)

[0023] In the above chemical formula 1, the M 1 is one type selected from the group consisting of Al and V, and -0.1≤y1<1, 0.000 <p1<0.500, 0.000<q1≤0.010, 0.000<q2≤0.010 이다.

[0024] (5) The present invention provides a positive electrode active material that further comprises a coating portion including carbon (C) formed on the lithium iron phosphate manganese-based compound in any one of (1) to (4).

[0025] (6) The present invention provides a positive electrode active material having an average crystallite size of 100 nm or more and 140 nm or less in any one of (1) to (5).

[0026] (7) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (6).

[0027] (8) The present invention provides a lithium secondary battery comprising a positive electrode according to (7) above.

[0028]

[0029]

[0030] The present invention aims to solve the above-mentioned problems by providing a positive electrode active material capable of reducing manganese leaching and improving the battery's lifespan, capacity, resistance, and charging efficiency.

[0031] In addition, the present invention aims to provide a positive electrode and a secondary battery having excellent lifespan characteristics and capacity characteristics, including the positive electrode active material as described above.

[0032]

[0033] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0034] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0035] In this specification, terms such as 'comprising,' 'having,' or 'having' are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0036] In this specification, the content of each element in the lithium iron phosphate-based compound may be measured through Inductive Coupled Plasma (ICP) analysis using an Inductively Coupled Plasma Emission Spectrometer (ICP-OES; Agilent 5900, Agilent).

[0037] In this specification, the average particle size (D 50 ) can be defined as the particle diameter corresponding to 50% of the cumulative volume distribution in the particle size distribution curve (graph curve of the particle size distribution). The above average particle diameter is obtained by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Mastersizer 3000, Malvern), calculating the particle size distribution by measuring the difference in diffraction patterns according to particle size as the particles pass through a laser beam, and calculating the particle diameter at the point where it is 50% of the cumulative volume distribution according to particle diameter in the measuring device, thereby D 50 It can measure.

[0038] In this specification, 'crystallite' refers to a particle unit having substantially the same crystal orientation.

[0039] In this specification, the 'average crystallite size' can be quantitatively analyzed using X-ray diffraction analysis (XRD) by Cu Kα X-rays. Specifically, XRD data of the synthesized cathode active material was obtained using a Bruker D8 XRD instrument (Cu-target, voltage: 45 kV, current: 40 mA, 2θ: 10° to 100°). Structural analysis of the obtained data was performed using the Rietveld refining method, a general structural analysis method, with software called Highscore from Malvern Panalytical.

[0040] The Rietveld refining method is a process that obtains a diffraction pattern calculated from an initial structural model of a material's crystal structure and compares it with the measured diffraction pattern of the actual synthesized material. It involves gradually and iteratively adjusting the material by introducing and changing various structure-related factors until the two patterns match well.

[0041] This method adopts an approach that repeats the process until the difference between the calculated and measured patterns is minimized, while determining validity based on the difference between the two patterns. Among the structure-related factors that can be introduced in this process, the crystal size can be determined using the full width at half maximum (FWHM) of the peaks of each crystal plane appearing in the measured diffraction pattern.

[0042]

[0043] positive electrode active material

[0044] Hereinafter, the positive active material according to the present invention will be described.

[0045]

[0046] The cathode active material according to the present invention comprises a lithium iron manganese phosphate compound having a manganese (Mn) content of less than 50 mol% among all metals excluding lithium, wherein the lithium iron manganese phosphate compound comprises magnesium (Mg) and a doping element (M), and the doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V), wherein the magnesium (Mg) content in the lithium iron manganese phosphate compound is 500 ppm or more and 1,500 ppm or less with respect to the total weight of the lithium iron manganese phosphate compound, and the average particle size (D 50 ) is between 400nm and 900nm.

[0047]

[0048] The inventors provide a lithium iron manganese phosphate compound having a manganese (Mn) content of less than 50 mol% among all metals excluding lithium, wherein the lithium iron manganese phosphate compound comprises magnesium (Mg) and a doping element (M), wherein the doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V), wherein the magnesium (Mg) content in the lithium iron manganese phosphate compound is 500 ppm or more and 1,500 ppm or less with respect to the total weight of the lithium iron manganese phosphate compound, and the average particle size (D 50 When the value is 400 nm or more and 900 nm or less, the manganese leaching amount of the positive electrode active material is reduced, and when applied to a battery, the lifespan characteristics of the battery can be improved, the initial resistance of the battery can be reduced, and the discharge capacity and charge efficiency can be improved, and the present invention was completed.

[0049]

[0050] The above-mentioned lithium iron phosphate manganese-based compound has a manganese (Mn) content of less than 50 mol% among the total metals excluding lithium. Specifically, the manganese (Mn) content may be greater than 0 mol%, 10 mol% or more, 15 mol% or more, 20 mol% or more, or 25 mol% or more, and may be 35 mol% or less, 40 mol% or less, 45 mol% or less, or less than 50 mol%. When the manganese (Mn) content among the total metals excluding lithium is within the above range, it has the effect of improving lifespan characteristics while reducing the amount of manganese leaching. In particular, when the manganese content is 25 mol% or more and 35 mol% or less, while maintaining lifespan characteristics, the average operating voltage increases due to manganese, and the discharge capacity is improved, resulting in improved energy density. When the manganese content is 50 mol% or more, there is a problem where the amount of manganese leaching increases and lifespan characteristics are inferior. Specifically, when charging and discharging, Mn 2+ / Mn 3+ The oxidation number of manganese changes, and since the structural symmetry of the atom changes depending on the oxidation number of manganese, there is a problem with the structure of the cathode active material becoming distorted, and unstable Mn 3+ There is a problem in that manganese leaches out of the positive active material by reacting with HF.

[0051]

[0052] The above lithium iron manganese phosphate compound comprises magnesium (Mg) and a doping element (M), wherein the doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V). When the lithium iron manganese phosphate compound comprises one or more selected from the group consisting of magnesium (Mg), aluminum (Al), and vanadium (V), the doping element strengthens the bond between manganese and oxygen, thereby reducing the distortion of the bond between manganese and oxygen. The doping element increases the bond length between lithium and oxygen, thereby securing a pathway for the movement of lithium ions to facilitate the insertion and extraction of lithium, and has the effect of suppressing the phase separation of the lithium iron manganese phosphate compound into a lithium iron phosphate compound and a lithium phosphate transition metal compound. Furthermore, the doping element reduces the electron band gap, thereby allowing electrons to easily move from the valence band to the conduction band.

[0053] Meanwhile, the element (MX), excluding magnesium (Mg) and the doping element (M), may be one or more selected from the group consisting of Y, Zr, K, Sr, Ba, B, Ce, Cr, F, Ti, Fe, Zn, Si, Nb, Ga, Sn, Mo, W, and P. The element (MX) may exist as an impurity in the lithium iron phosphate manganese-based compound during the manufacturing process, and the impurity form does not significantly affect the battery characteristics. The impurity form is a concept distinct from the doping element and means that the molar ratio of the element among the total metals excluding lithium in the lithium iron phosphate manganese-based compound is 0.01 mol% or less.

[0054] On the other hand, if the lithium iron manganese phosphate compound does not contain both magnesium and a doping element (M), or contains only magnesium (Mg) or a doping element (M), the bond between manganese and oxygen is weak, so the bond between manganese and oxygen is easily twisted, the bond length between lithium and oxygen is short, making it difficult to insert and extract lithium ions, and the lithium iron manganese phosphate compound tends to phase-separate into a lithium iron phosphate compound and a lithium manganese phosphate compound, and the electron band gap is large, making electron movement difficult, so there are problems with inferior output characteristics, capacity characteristics, and lifespan characteristics of the battery containing it. In addition, if the lithium iron manganese phosphate compound contains magnesium and a doping element, but the doping element is not one selected from the group consisting of aluminum (Al) and vanadium (V), the bond between manganese and oxygen is not strengthened, the bond length between lithium and oxygen is not increased, and the electron band gap is not reduced, so there are problems with inferior lifespan characteristics, capacity characteristics, and output characteristics of the battery containing it.

[0055] The magnesium (Mg) content in the above lithium iron phosphate manganese-based compound is 500 ppm or more and 1,500 ppm or less with respect to the total weight of the above lithium iron phosphate manganese-based compound. Specifically, the magnesium (Mg) content in the above lithium iron phosphate manganese-based compound may be 500 ppm or more, 600 ppm or more, or 700 ppm or more, and 1,400 ppm or less, or 1,500 ppm or less with respect to the total weight of the above lithium iron phosphate manganese-based compound. When the magnesium content is within the above range, the lifespan characteristics, capacity characteristics, and output characteristics are improved due to the effect of strengthening the bond between manganese and oxygen to reduce the distortion of the bond between manganese and oxygen, and the effect of magnesium increasing the bond length between lithium and oxygen to secure a pathway for the movement of lithium ions, thereby facilitating the insertion and extraction of lithium, and suppressing the phase separation of the lithium iron phosphate manganese-based compound into a lithium iron phosphate compound and a lithium metal phosphate compound. When the magnesium (Mg) content in the above-mentioned lithium iron phosphate manganese-based compound is less than 500 ppm relative to the total weight of the lithium iron phosphate manganese-based compound, there is a problem in that it is difficult to secure a pathway for the movement of lithium ions because the bond length between lithium and oxygen is short, and when the magnesium (Mg) content in the above-mentioned lithium iron phosphate manganese-based compound is more than 1,500 ppm relative to the total weight of the lithium iron phosphate manganese-based compound, the interaction between magnesium (Mg) ions becomes excessive, causing the crystal lattice structure to be excessively deformed and resulting in a problem of inferior capacity retention rate.

[0056] And, the above positive active material has an average particle size (D 50 ) is 400 nm or more and 900 nm or less. Specifically, the above-mentioned positive electrode active material has an average particle size (D 50) may be 400 nm or more, or 450 nm or more, and may be 550 nm or less, 600 nm or less, 650 nm or less, or 700 nm or less, 750 nm or less, 800 nm or less, 850 nm or less, or 900 nm or less. Average particle size (D 50 If ) is within the above range, there is an effect of increasing rolling density and discharge capacity. Average particle size (D 50 If ) is less than 400 nm, there is a problem of inferior electrode processability due to the increase in specific surface area, and the average particle size (D 50 If ) exceeds 900 nm, there is a problem with reduced rolling density and inferior discharge capacity.

[0057]

[0058] According to one embodiment of the present invention, the content of the doping element (M) in the lithium iron phosphate manganese-based compound may be 800 ppm or more and 5,000 ppm or less with respect to the total weight of the lithium iron phosphate manganese-based compound. Specifically, the content of the doping element (M) in the lithium iron phosphate manganese-based compound may be 800 ppm or more with respect to the total weight of the lithium iron phosphate manganese-based compound, and may be 3,300 ppm or less, 3,400 ppm or less, 3,500 ppm or less, 3,600 ppm or less, 3,700 ppm or less, 3,800 ppm or less, 3,900 ppm or less, 4,000 ppm or less, 4,100 ppm or less, 4,200 ppm or less, 4,300 ppm or less, 4,400 ppm or less, 4,500 ppm or less, 4,600 ppm or less, 4,700 ppm or less, 4,800 ppm or less, 4,900 ppm or less, or 5,000 ppm or less. When the content of the above doping element (M) is within the above range, the lifespan characteristics, capacity characteristics, and output characteristics are improved due to the effect of strengthening the bond between manganese and oxygen to reduce the distortion of the bond between manganese and oxygen, and the effect of increasing the bond length between lithium and oxygen by the doping element (M) to secure a pathway for the movement of lithium ions, thereby facilitating the insertion and extraction of lithium and suppressing the phase separation of the lithium iron phosphate manganese-based compound into a lithium iron phosphate compound and a lithium metal phosphate compound.

[0059]

[0060] According to one embodiment of the present invention, the lithium iron phosphate manganese-based compound may have a composition represented by the following chemical formula 1.

[0061] [Chemical Formula 1]

[0062] Li 1+y1 Fe1-p1-q1-q2Mn p1 Mg q1 M 1 q2 (PO4)

[0063] In the above chemical formula 1, the M 1 is one type selected from the group consisting of Al and V, and -0.1≤y1<1, 0.000 <p1<0.500, 0.000<q1≤0.010, 0.000<q2≤0.010 이다.

[0064] In the above chemical formula 1, the M 1 The doping element may be, specifically, one selected from the group consisting of Al and V. The above M 1 is necessarily included.

[0065] Meanwhile, the above y1, p1, q1, and q2 may have up to three decimal places as significant figures.

[0066] The above y1 may be -0.1 or greater, or 0.0 or greater, and 0.05 or less, or 0.1 or less. When y1 satisfies the above range, structural stability may be improved.

[0067] The above p1 is the mole fraction of manganese (Mn) among all metals excluding lithium in the lithium iron phosphate manganese-based compound, and may be greater than 0.000, greater than 0.050, greater than 0.100, greater than 0.150, greater than 0.200, or greater than 0.250, and may be less than 0.300, less than 0.350, less than 0.400, less than 0.450, or less than 0.500. When the above p1 satisfies the above range, high energy density is exhibited, and high capacity characteristics can be realized.

[0068] The above q1 is the mole fraction of Mg among all metals excluding lithium in the lithium iron phosphate manganese-based compound, and may be greater than 0.000, greater than 0.001, greater than 0.002, greater than 0.003, or greater than 0.004, and may be less than 0.005, less than 0.006, less than 0.007, less than 0.008, less than 0.009, or less than 0.010. When the above q1 satisfies the above range, the average operating voltage increases, the discharge capacity is improved, and the energy density is improved, while life characteristics can be improved by controlling the length and strength of the bond between manganese and oxygen and the bond between lithium and oxygen.

[0069] The above q2 is M among the total metals excluding lithium in the lithium iron phosphate manganese-based compound. 1 The mole fraction may be greater than 0.000, greater than or equal to 0.001, greater than or equal to 0.002, greater than or equal to 0.003, or greater than or equal to 0.004, and less than or equal to 0.005, less than or equal to 0.006, less than or equal to 0.007, less than or equal to 0.008, less than or equal to 0.009, or less than or equal to 0.010. When the above q2 satisfies the above range, the average operating voltage increases, the discharge capacity is improved, and the energy density is improved, while the life characteristics can be improved by controlling the length and strength of the bond between manganese and oxygen and the bond between lithium and oxygen.

[0070]

[0071] According to one embodiment of the present invention, the coating portion comprising carbon (C) formed on the lithium iron phosphate manganese-based compound may be further included. By further including the coating portion comprising carbon (C), the electron conductivity of the positive electrode active material can be improved.

[0072] Meanwhile, the content of carbon (C) included in the coating portion may be greater than 0 weight% and less than or equal to 5 weight% with respect to the total weight of the positive electrode active material. Specifically, the content of carbon (C) included in the coating portion may be greater than 0 weight%, 1 weight% or more, 2 weight% or more, or 3 weight% or more, and 4 weight% or less, or 5 weight% or less. When the content of carbon (C) included in the coating portion is within the above range, it may improve the electron conductivity of the positive electrode active material without acting as a resistor.

[0073]

[0074] According to one embodiment of the present invention, the positive electrode active material may have an average crystallite size of 100 nm or more and 140 nm or less. Specifically, the average crystallite size may be 100 nm or more, 130 nm or less, 135 nm or less, or 140 nm or less. When the average crystallite size is within the above range, the electrical conductivity and ionic conductivity are improved, thereby having the effect of improving the capacity characteristics and rate characteristics of the positive electrode active material.

[0075]

[0076] The positive electrode active material of the present invention can be manufactured according to conventional methods in the art. For example, it can be manufactured by calcining raw materials and lithium-containing raw materials.

[0077] Specifically, the positive electrode active material of the present invention can be manufactured by a method for manufacturing a positive electrode active material comprising: (a) a step of preparing a mixture by mixing a lithium-containing raw material, iron phosphate (FePO4), a manganese-containing raw material, a phosphoric acid-containing raw material, a magnesium (Mg)-containing raw material, and a doping element (M)-containing raw material (wherein the doping element (M) is one selected from the group consisting of Al and V); and (b) a step of preparing a lithium iron phosphate manganese-based compound by calcining the mixture.

[0078] The above lithium-containing raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the above lithium-containing raw material may be at least one selected from the group consisting of Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, and Li3C6H5O7, and any one or more of these may be used.

[0079] The above manganese (Mn)-containing raw material may be at least one selected from the group consisting of MnSO4, MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citric acid, manganese fatty acid salts, oxyhydroxides, and manganese chloride halides, and one or more of these may be used.

[0080] The above magnesium (Mg)-containing raw material may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing magnesium (Mg), and one or more of these may be used.

[0081] The raw material containing the doping element (M) may be at least one selected from the group consisting of oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and halides containing one doping element (M) selected from the group consisting of Al and V, and one or more mixtures of these may be used.

[0082] According to the present invention, in step (a), the lithium-containing raw material, iron phosphate (FePO4), manganese-containing raw material, phosphoric acid-containing raw material, magnesium (Mg)-containing raw material, and doping element (M)-containing raw material (wherein the doping element (M) is one selected from the group consisting of Al and V) may be mixed in an amount such that they have a composition represented by Chemical Formula 1 as described in the present specification.

[0083] After step (a) above, it may include a step of additionally mixing carbon-containing raw materials.

[0084] The carbon-containing coating material may be one or more selected from sucrose, glucose, polyethylene glycol, polyvinyl alcohol, and polyvinyl acetate.

[0085] The carbon-containing raw material may be mixed in an amount greater than 0 parts by weight and less than or equal to 10 parts by weight with respect to 100 parts by weight of the total weight of the lithium-containing raw material, iron phosphate, manganese-containing raw material, and phosphoric acid-containing raw material.

[0086] Step (b) above may involve calcining the mixture at a temperature of 600°C or higher and 800°C or lower to produce a lithium iron phosphate manganese-based compound.

[0087]

[0088] anode

[0089] Next, the anode according to the present invention will be described.

[0090] The anode according to the present invention comprises an anode active material layer comprising an anode active material according to the present invention. Specifically, the anode comprises an anode current collector and an anode active material layer formed on the anode current collector and comprising the anode active material. Since the anode active material has been described above, a detailed explanation is omitted, and only the remaining components are described in detail below.

[0091]

[0092] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0093]

[0094] The above positive active material layer may include a conductive material and a binder together with the positive active material. In this case, the positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0095]

[0096] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0097]

[0098] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight based on the total weight of the positive active material layer.

[0099]

[0100] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it may be manufactured by applying a composition for forming an anode active material layer, prepared by dissolving or dispersing the above-described anode active material and, optionally, a binder and a conductive material in a solvent, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above. Alternatively, the above-described anode may be manufactured by casting the composition for forming an anode active material layer onto a separate support, and then laminating the film obtained by peeling from the support onto an anode current collector.

[0101]

[0102] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0103]

[0104] lithium secondary battery

[0105] Next, a lithium secondary battery according to the present invention will be described.

[0106]

[0107] The present invention can manufacture an electrochemical device comprising the anode. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0108]

[0109] Specifically, the above lithium secondary battery comprises a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Since the positive electrode is identical to the one described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0110]

[0111] In addition, the lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0112]

[0113] In the above lithium secondary battery, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0114] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0115]

[0116] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0117]

[0118] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0119] The above-mentioned negative electrode active material may be included in an amount of 80% to 99% by weight relative to the total weight of the negative electrode active material layer.

[0120]

[0121] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight relative to the total weight of the negative active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0122]

[0123] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, specifically 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0124]

[0125] The above-mentioned negative electrode active material layer may be manufactured by applying and drying a composition for forming a negative electrode active material layer, prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent, or by casting the composition for forming a negative electrode active material layer onto a separate support and then laminating the film obtained by peeling from the support onto a negative electrode current collector.

[0126]

[0127] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries can be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0128]

[0129] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0130] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0131] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; and carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC). Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond-directing ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate-based solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0132]

[0133] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, specifically 0.1 to 3.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0134]

[0135] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 10 weight%, specifically 0.1 to 5 weight%, based on the total weight of the electrolyte.

[0136]

[0137] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent lifespan and capacity characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0138] Accordingly, according to another embodiment of the present invention, a battery module comprising the lithium secondary battery as a unit cell and a battery pack comprising the same are provided.

[0139] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0140] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0141] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0142]

[0143] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0144]

[0145] Examples and Comparative Examples

[0146] Example 1

[0147] Li2CO 3, MnCO3, FePO4, NH4H2PO4, MgO, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:Mg:V:PO4 was 1:0.3:0.7:0.005:0.005:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0148] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0149] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.693 Mg 0.005 V 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0150]

[0151] Example 2

[0152] Li2CO 3, MnCO3, FePO4, NH4H2PO4, MgO, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:Mg:V:PO4 was 1:0.3:0.7:0.005:0.01:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0153] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0154] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.294 Fe 0.691 Mg 0.005 V 0.01 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0155]

[0156] Example 3

[0157] Li2CO 3, MnCO3, FePO4, NH4H2PO4, MgO, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:Mg:V:PO4 was 1:0.3:0.7:0.01:0.005:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0158] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0159] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.294 Fe 0.691 Mg 0.01 V 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0160]

[0161] Example 4

[0162] Li2CO 3, MnCO3, FePO4, NH4H2PO4, MgO, and Al(OH)3 were mixed such that the molar ratio of Li:Mn:Fe:Mg:Al:PO4 was 1:0.3:0.7:0.01:0.005:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0163] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0164] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.294 Fe 0.691 Mg 0.01 Al 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0165]

[0166] Comparative Example 1

[0167] A positive electrode active material was prepared by performing the same procedure as in Example 1, except that MgO and V2O5 were not mixed.

[0168]

[0169] Comparative Example 2

[0170] Li2CO 3,MnCO3, FePO4, NH4H2PO4, MgO, and TiO2 were mixed such that the molar ratio of Li:Mn:Fe:Mg:Ti:PO4 was 1:0.3:0.7:0.005:0.005:1, and a mixture was prepared by mixing in sucrose. At this time, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0171] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0172] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.693 Mg 0.005 Ti 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0173]

[0174] Comparative Example 3

[0175] Li2CO 3, MnCO3, FePO4, NH4H2PO4, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:V:PO4 was 1:0.3:0.7:0.01:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0176] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0177] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.693 V 0.01 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0178]

[0179] Comparative Example 4

[0180] Li2CO 3, MnCO3, FePO4, NH4H2PO4, and MgO were mixed such that the molar ratio of Li:Mn:Fe:Mg:PO4 was 1:0.3:0.7:0.01:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0181] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0182] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.693 Mg 0.01 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0183]

[0184] Comparative Example 5

[0185] Li2CO 3,MnCO3, FePO4, NH4H2PO4, and TiO2 were mixed such that the molar ratio of Li:Mn:Fe:Ti:PO4 was 1:0.3:0.7:0.01:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0186] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0187] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.693 Ti 0.01 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0188]

[0189] Comparative Example 6

[0190] Except for calcining at a temperature of 800°C instead of 700°C, the procedure was carried out in the same manner as Comparative Example 5, and LiMn 0.297 Fe 0.693 Ti 0.01 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0191]

[0192] Comparative Example 7

[0193] Li2CO 3,MnCO3, FePO4, NH4H2PO4, MgO, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:Mg:V:PO4 was 1:0.3:0.7:0.004:0.005:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0194] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0195] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.297 Fe 0.694 Mg 0.004 V 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0196]

[0197] Comparative Example 8

[0198] Li2CO 3, MnCO3, FePO4, NH4H2PO4, MgO, and V2O5 were mixed such that the molar ratio of Li:Mn:Fe:Mg:V:PO4 was 1:0.5:0.5:0.015:0.005:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0199] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0200] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 700℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.491 Fe 0.489 Mg 0.015 V 0.005 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0201]

[0202] Comparative Example 9

[0203] Li2CO 3, MnCO3, FePO4, NH4H2PO4, and MgO were mixed such that the molar ratio of Li:Mn:Fe:Mg:PO4 was 1:0.5:0.5:0.02:1, and a mixture was prepared by mixing in sucrose. In this case, the sucrose was Li2CO 3, MnCO3, FePO4, and NH4H2PO4 are mixed in an amount of 5 parts by weight per 100 parts by weight of total weight.

[0204] Subsequently, the above mixture and water are mixed to obtain a solid content concentration of 40 wt%, and then wet-milled in a bead mill for 1 hour to obtain a slurry (D 50 : 200nm) was manufactured.

[0205] After spray-drying the above slurry (inlet temperature 250℃, outlet temperature 95℃), it is calcined at a temperature of 800℃ for 8 hours under a nitrogen atmosphere to produce LiMn 0.496 Fe 0.494 Mg 0.02 A positive electrode active material was prepared by forming a carbon (C) coating portion on a lithium iron phosphate manganese-based compound having a composition represented by PO4.

[0206]

[0207] Experimental Example

[0208] Experimental Example 1: ICP Analysis

[0209] For the positive electrode active materials prepared in the above examples and comparative examples, the composition of the positive electrode active material and the content of magnesium and doping element (M) were determined by the following method and are shown in Table 1 below.

[0210] Specifically, 1 ml of hydrochloric acid was added to 0.1 g of each positive active material particle prepared in the above examples and comparative examples, and heated to dissolve the positive active material. Subsequently, a small amount of hydrogen peroxide was added to promote the reaction and completely dissolve the positive active material to prepare a solution. Then, the solution was diluted with deionized water to a total volume of 10 ml to prepare an analytical sample. Using ICP-OES (Aligent 5900, Aligent), the composition of the positive active material and the weight (ppm) of magnesium and doping element (M) present in the analytical sample were confirmed and are shown in Table 1 below.

[0211]

[0212] Classification Composition Type of Element Weight (ppm) Example 1 LiMn 0.297 Fe 0.693 Mg 0.005 V 0.005 PO4Mg700V1,550 Example 2LiMn 0.294 Fe 0.691 Mg 0.005 V 0.010 PO4Mg760V3,220 Example 3LiMn 0.294 Fe 0.691 Mg 0.010 V 0.005 PO4Mg 1,300V 1,400 Example 4LiMn 0.294 Fe 0.691 Mg 0.010 Al 0.005 PO4Mg 1,400Al800 Comparative Example 1LiMn 0.300 Fe 0.700 PO4--Comparative Example 2LiMn 0.297 Fe 0.693 Mg 0.005 Ti 0.005 PO4Mg700Ti1,500 Comparative Example 3LiMn 0.297 Fe 0.693 V 0.010PO4V3,100 Comparative Example 4LiMn 0.297 Fe 0.693 Mg 0.010 PO4Mg1,400 Comparative Example 5LiMn 0.297 Fe 0.693 Ti 0.010 PO4Ti3,070 Comparative Example 6LiMn 0.297 Fe 0.693 Ti 0.010 PO4Ti3,070 Comparative Example 7LiMn 0.294 Fe 0.694 Mg 0.004 V 0.005 PO4Mg400V1,300 Comparative Example 8LiMn 0.491 Fe 0.489 Mg 0.015 V 0.005 PO4Mg 2,000V 1,300 Comparative Example 9LiMn 0.496 Fe 0.494 Mg 0.020 PO4Mg2,800

[0213] Through Table 1, it was confirmed that the lithium iron manganese phosphate compounds prepared in Examples 1 to 4 have a composition represented by Formula 1 described in this specification, and that the magnesium (Mg) content in the lithium iron manganese phosphate compounds is 500 ppm or more and 1,500 ppm or less relative to the total weight of the lithium iron manganese phosphate compounds, and that the vanadium (V) or aluminum (Al) content in the lithium iron manganese phosphate compounds is 800 ppm or more and 5,000 ppm or less relative to the total weight of the lithium iron manganese phosphate compounds. On the other hand, it was confirmed that the iron manganese phosphate compounds prepared in Comparative Examples 1, 5, and 6 do not contain magnesium (Mg) and doping elements (M), and that the cathode active materials prepared in Comparative Examples 2 to 4 and 9 do not contain doping elements (M) or magnesium. In addition, it was confirmed that the positive electrode active material prepared in Comparative Examples 7 and 8 had a magnesium (Mg) content in the lithium iron phosphate manganese-based compound of less than 500 ppm or more than 1,500 ppm relative to the total weight of the lithium iron phosphate manganese-based compound.

[0214]

[0215] Experimental Example 2: PSA Analysis

[0216] The average particle size (D) of each cathode active material prepared in the examples and comparative examples using a PSA (Mastersizer 3000, Malvern) 50 )(nm) was measured, and the results are shown in Table 2 below.

[0217]

[0218] Classification average particle size (D 50 )(nm) Example 1477 Example 2500 Example 3533 Example 4452 Comparative Example 1620 Comparative Example 2509 Comparative Example 3478 Comparative Example 4452 Comparative Example 5389 Comparative Example 61180 Comparative Example 7718 Comparative Example 8817 Comparative Example 91680

[0219] Through Table 2, the cathode active materials prepared in Examples 1 to 4 have an average particle size (D 50 It was confirmed that ) was between 400 nm and 900 nm. On the other hand, the cathode active material prepared in Comparative Example 5 had an average particle size (D 50 ) is less than 400 nm, and the cathode active materials prepared in Comparative Examples 6 and 9 have an average particle size (D 50 It was confirmed that ) exceeded 900nm.

[0220]

[0221] Experimental Example 3: XRD Analysis

[0222] XRD data analysis was performed after XRD measurement for each cathode active material prepared in the examples and comparative examples, and the average crystallite size (nm) is shown in Table 3 below.

[0223] Specifically, the XRD measurement was performed using a Bruker D8 XRD instrument, and 2 to 3 g of positive active material particles were taken from the positive active material powder and measured at a scan speed of 0.2 ° / sec from 2θ: 10° to 100° under conditions of Cu-Kα line (wavelength 1.54 Å), acceleration voltage 45 kV, and current 40 mA.

[0224] Classification Average Determinant Size (nm) Example 1 109 Example 2 127 Example 3 122 Example 4 103 Comparative Example 1 130 Comparative Example 2 123 Comparative Example 3 104 Comparative Example 4 103 Comparative Example 596 Comparative Example 6 173 Comparative Example 7 139 Comparative Example 8 125 Comparative Example 955

[0225] Through Table 3, it was confirmed that the cathode active materials prepared in Examples 1 to 4 had an average crystallite size of 100 nm or more and 140 nm or less. On the other hand, it was confirmed that the cathode active materials prepared in Comparative Examples 5 and 9 had an average crystallite size of less than 100 nm, and the cathode active material prepared in Comparative Example 6 had an average crystallite size of more than 140 nm.

[0226]

[0227] Experimental Example 4: Evaluation of Battery Characteristics

[0228] - Coin-type half-battery manufacturing

[0229] An anode slurry was prepared by mixing 90 wt% of the anode active material prepared in the above examples and comparative examples, 5.0 wt% of carbon black as a conductive material, and 5.0 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The anode slurry prepared above was coated on one side of an aluminum current collector, dried at 100°C, and then rolled to produce an anode.

[0230] An electrode assembly was manufactured by using a lithium metal electrode as the negative electrode and interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution in which 1.0 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0231] After manufacturing a coin-type half-cell, the battery life and discharge capacity evaluations were performed by following the method.

[0232]

[0233] - Battery life evaluation

[0234] A total of 30 cycles of charging and discharging were repeated, with one cycle consisting of charging to 4.25V at 45℃ using the CC-CV method (0.5C) followed by discharging to 2.5V using the CC method (1.0C). After measuring the discharge capacity in the first and 30th cycles, the percentage of the discharge capacity of the 30th cycle relative to the discharge capacity of the first cycle (45℃ high temperature cycle life (%)) was calculated and is shown in Table 4 below.

[0235]

[0236] Classification 45℃ High Temperature Cycle Life (%) Example 199.7 Example 299.5 Example 399.8 Example 499.7 Comparative Example 198.7 Comparative Example 299.2 Comparative Example 399.4 Comparative Example 498.2 Comparative Example 597.2 Comparative Example 698.8 Comparative Example 797.3 Comparative Example 898.4 Comparative Example 991.4

[0237] Through Table 4, it was confirmed that the battery containing the positive active material prepared in Examples 1 to 4 had a superior high-temperature cycle life compared to the battery containing the positive active material prepared in Comparative Examples 1 to 9.

[0238] - Battery initial discharge capacity evaluation

[0239] For the above coin-type half-cell, it was charged (0.1C) to 4.25 V using the CC-CV method at 25 ℃, then discharged (1.0C) to 2.5 V using the CC method after a 24-hour rest, and the discharge capacity (mAh / g) at that time was measured and is shown in Table 5 below.

[0240] Classification Initial Discharge Capacity (mAh / g) Example 1 158.4 Example 2 156.3 Example 3 158.4 Example 4 155.6 Comparative Example 1 146.4 Comparative Example 2 155.7 Comparative Example 3 155.5 Comparative Example 4 155.6 Comparative Example 5 154.9 Comparative Example 6 122.4 Comparative Example 7 153.8 Comparative Example 8 143.6 Comparative Example 9 148.7

[0241] Through Table 5, it was confirmed that the initial discharge capacity of the battery containing the positive active material prepared in Examples 1 to 4 was significantly superior to that of the battery containing the positive active material prepared in Comparative Examples 1 to 9. Meanwhile, it was confirmed that there was a significant difference in the initial discharge capacity in Comparative Examples 5 and 6, which have the same composition but different average particle sizes.

[0242] In conclusion, the positive electrode active material according to the present invention simultaneously satisfies the composition and average particle size, thereby securing a lithium migration pathway while improving structural stability and increasing rolling density. Consequently, it can be seen that the energy density of the battery can be improved, irreversible capacity loss during charging and discharging is minimized, and the battery remains relatively stable even during charge-discharge cycles.

Claims

1. Includes a lithium iron phosphate manganese-based compound in which the manganese (Mn) content among all metals excluding lithium is less than 50 mol%, and The above lithium iron phosphate manganese-based compound comprises magnesium (Mg) and a doping element (M), and The above doping element (M) is one selected from the group consisting of aluminum (Al) and vanadium (V), and The magnesium (Mg) content in the above lithium iron phosphate manganese-based compound is 500 ppm or more and 1,500 ppm or less with respect to the total weight of the above lithium iron phosphate manganese-based compound, and Average particle size (D 50 A positive electrode active material having a diameter of 400 nm or more and 900 nm or less.

2. In Claim 1, The above lithium iron phosphate manganese-based compound is a positive electrode active material having a manganese (Mn) content of 25 mol% or more and 35 mol% or less among all metals excluding lithium.

3. In Claim 1, A positive electrode active material in which the content of a doping element (M) in the above lithium iron phosphate manganese-based compound is 800 ppm or more and 5,000 ppm or less with respect to the total weight of the above lithium iron phosphate manganese-based compound.

4. In Claim 1, The above lithium iron phosphate manganese-based compound is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li 1+y1 Fe1-p1-q1-q2Mn p1 Mg q1 M 1 q2 (PO4) In the above chemical formula 1, The above M 1 is one type selected from the group consisting of Al and V, and -0.1≤y1<1, 0.000 <p1<0.500, 0.000<q1≤0.010, 0.000<q2≤0.010 이다.

5. In Claim 1, A positive electrode active material further comprising a coating portion containing carbon (C) formed on the above-mentioned lithium iron phosphate manganese-based compound.

6. In Claim 1, A positive electrode active material having an average crystallite size of 100 nm or more and 140 nm or less.

7. An anode comprising an anode active material according to any one of claims 1 to 6.

8. A lithium secondary battery comprising a positive electrode according to claim 7.